Waxes are organic compounds that have long alkyl chains. Animal waxes, vegetable waxes, and petroleum waxes are derived from natural sources. The basic structural unit of natural oils and fats, for example, is a triglyceride, which is an ester of glycerol with three fatty acid molecules having the structure below:
wherein R1, R2, and R3 represent C4-C30 hydrocarbon chains, some of which have unsaturation. Fatty acids are carboxylic acids containing long linear hydrocarbon chains. Lengths of the hydrocarbon chains most commonly are 18 carbons (C18). C18 fatty acids are typically bonded to the middle hydroxyl group of glycerol. Typical carbon numbers of the fatty acids linked to the two other hydroxyl groups are even numbers, being between C14 and C22. Waxes from natural sources account for 87% of the worldwide wax market. However, for environmental, economical, and regulatory reasons, it is of interest to produce waxes from renewable sources. Synthetic waxes, derived from petroleum or natural gas (a GTL process), are long-chain hydrocarbons lacking functional groups. Synthetic waxes account for 10% of the worldwide wax market.
The renewable waxes derived from animal and vegetable sources typically have a mixture of hydrocarbons, alcohols, free acids and esters. These vegetable and animal based waxes account for only 3% of the global wax market. Recently, there has been a growing demand for renewable waxes as a result of a declining supply of petroleum based waxes, increased paraffin wax prices, and a growing consumer preference for bio-derived products. Natural renewable waxes, however, such as bee's wax, are very expensive.
Microcrystalline waxes/petrolatum waxes derived from fossil fuel sources are widely used in adhesives, coatings, cosmetics and personal care products. The branched structure of the carbon chain backbone in such waxes allows oil molecules to be incorporated into the crystal lattice structure. For use in candles, current approaches to incorporate renewable waxes include mixing of partially hydrogenated, refined and bleached triglyceride (mainly from soybean oil) with fully hydrogenated natural oils and/or free fatty acids. This will lead to a candle wax composition wherein the carbon chain length of the renewable wax molecule is limited to C14-C22 chains, depending on the source of the triglyceride oil. These wax molecules also have a polarity but are heavily crystalline and may frequently cause highly polar compounds, such as candle scent compounds to be excreted to the outer edges of the candle. Also, such small molecular weight waxes derived from renewable sources do not have adequate properties similar to microcrystalline waxes (such as high viscosity, oil content etc.) to be suitable in several adhesive, coatings and personal care product applications.
A further approach towards renewable wax is the metathesis of vegetable oils leading to dimers and trimers of triglycerides. A disadvantage to this approach is the high oxygen content of the wax, as each triglyceride unit contains 3 ester bonds, averaging to an oxygen content of approximately 9-12 wt %. Although polar, these compounds do not possess enough nonpolar character for wide use in a variety of applications involving polar waxes, for example, in adhesives, candles or personal care products.
Accordingly, there is a need for novel polar waxes derived from renewable sources, particularly to substitute high molecular weight microcrystalline waxes in the C40-C90 carbon chain length range, methods of forming polar waxes, and compositions comprising polar waxes.
References of interest include: U.S. Pat. No. 6,824,572 A1; U.S. Pat. No. 7,128,766 A1; U.S. Pat. No. 8,202,329 A1; U.S. Pat. No. 8,529,924 A1; U.S. Pat. No. 7,731,767 A1; U.S. Pat. No. 8,362,125 A1; U.S. Pat. No. 8,652,221; U.S. 2007/0249771 A1; U.S. Pat. No. 6,063,144; U.S. 2013/0178640; U.S. Pat. No. 8,157,873 A1; EP 0457665; U.S. Pat. No. 8,048,290 A1; U.S. Pat. No. 8,053,614 A1; U.S. 2014/0024869 A1; U.S. 2014/0142356 A1; U.S. Pat. No. 9,587,180 A1; U.S. 2014/0171699 A1.